ROLE OF ENDOCRINE

SYSTEM IN INSECTS

Presented By:

Varun Saini

13-503-014

MSc(ENTOMOLOGY)

TNAU,CBE-3

What are ENDOCRINE GLANDS? • GLANDS WITHOUT DUCT.• A gland that produces and secretes hormones

with in the body.

• Diffuses to haemolymph

• Also called as RETRO-CEREBRAL

GLANDS

What is HORMONE ?

• Greek word means ‘I EXCITE’.

• It is defined as Chemicals produced in a gland that are released into the blood and have their effect somewhere else in the animal.

COMPONENTS OF ENDOCRINE SYSTEM

• Neurosecretory

cells

• Corpora cardiaca

• Corpora allata

• Prothroracic

glandsThe Cerebral Neurosecretory Cells and Corpora cardiaca form a Neurosecretory system.

Prothoracic glands------Produce

Ecdysone.

Corpora allata-------------Produces JH.Corpora cardiaca---------Stores and releases brain

hormones. Also produces and releases some peptides such as Adipokinetic Hormones.

Midgut endocrine cells----Produce various

peptides. Epitracheal glands------Produce the ecdysis triggering hormone “Eclosion” in Lepidoptera

Neurosecretory cells----Produce Neurosecretion

ENDOCRINE GLANDS IN INSECTS

Major physiological functions regulated by NEUROHORMONES

(PTTH)

PROTOCEREBRUM

1. Neurosecretory cells (NSC)• NSC in dorsal part of

protocerebrum produce a hormone called Prothoracicotropic Hormone (PTTH) or BRAIN HORMONE which activates prothoracic glands.

• NSC in brain secretes BURSICON which is involved in hardening and darkening of cuticle.

• Neurosecretory cells scattered in the ventral nerve cord produce Diuretic Hormone.

In insects, the NEUROSECRETORY CELLS are responsible for production of hormones, except Ecdysone and Juvenile hormones, which are produced from Non-neural Tissues like Prothoracic Glands and Corpora Allata.

Insect NSCs shows Excitatory and Inhibitory post- synaptic potentials.

The release of hormone is mediated through the influx of Ca2+ ions.

Neurosecretory hormone that controls Tanning or Sclerotization and mechanical properties of the cuticle during and after a molt. Found in most ganglia of the CNS.

BURSICON

SCLEROTIZATION IN FLY PUPAE

Functional significance of

NEUROSECRETORY HORMONES

• The Growth and Reproduction in insects are undoubtedly under the control of neurosecretory hormones

• Neurosecretory hormones have also been associated with behavioural activities, such as, response of the female towards the male, cocoon formation etc.

Found in most of insects except COLLEMBOLA

Lies on each side of Aorta behind brain

Connected to protocerbrum and hypocerbral ganglion

It acts as a Conventional Storage and release organ for neurosecretory cells

It controls heart beat and regulate trehalose level in haemolymph

2. Corpora cardiaca(CC)

3. Corpora allata(CA)• These glands were discovered as early as 1899 by JANET

• A special type with both CC and CA fused and connected by the fused PG to form a single structure is represented by the RING GLAND in CYCLORRHAPHOUS DIPTERA

• CA hormones are responsible for the inhibition of metamorphosis. The CA hormone(s) is therefore sometimes also called as ‘Inhibitory or Status Quo’ Hormone

• Secretes JUVENILE HORMONE (JH) OR NEOTININ there by inhibit metamorphosis (adult characteristics)

SER is structural site for JH regulation

A decreasing activity of corpora allata during successive larval instars resulting in the virtual cessation of activity in the last instar.

Other activities controlled by CA are polymorphism, regeneration, metabolism of fat, water balance, colour changes, imaginal diapause, pheromone production etc.

JH first extracted from the abdomen of Hyalophora cercopia (Moth)

It is needed for egg maturation and function as accessory glands

Use of juvenile hormone and their mimics in pest control •The concept of juvenile hormone and their mimics as insecticide was developed in a startling way when Dr. Karl Slama of Prague went to Harvard to collaborate with Professor Carroll Williams.

• Slama took a stock of the bug Pyrrhocoris apterus with him but he found that in Harvard the bugs would not develop into normal adult•A comparison between the culture conditions in Harvard and Prague eventually revealed that paper towels used in rearing jars were the source of the substance.

• The substance was called as ‘PAPER FACTOR’ which chemically show resemblance to JH.

• JH and their analogues have already shown interesting results against Tribolium infestation.

Carroll Williams and John Law getting the “Paper Factor” from brown paper towels

PAPER FACTOR

Normal Case

Paper Factor Case

• METHOPRENE (Ist Commercial Product) is used in Mosquito control.

• HYDROPRENE and KINOPRENE are JH analogues and are used in insect control

• JH I is found mainly in the Lepidoptera Manduca sexta

• JH III was discovered by DR. YIN Found mainly in the CYCLORRHAPHOUS DIPTERANS.

JUVENOIDS

Fenoxycarb - Fruit Pests.Pyriproxyfen - Sucking PestsDiofenolan - Lepidopteran Pests.NC-196 - BPH of Rice.JH treated immature insects fail to moult, died soon after ecdysis ,fail to reproduce and develop in b/w larva & pupa Pupa & adult or larvae & adult.

OTHER JUVENOIDS

PRECOCENE-from the common Bedding plant, Ageratum houstonianum

Corpora allata

Corpora allata

Healthy

Infected

(Before Precocene injection)

(After Precocene injection)

CA in adult Phormia reginaANTIHORMONES

Paired gland present in ventro lateral part of prothorax of larva Also called as Pericardial or Ecdysial Gland Degenerated in adults Secretes the moulting hormone ECDYSONE Neurosecretory cells (NSC) activate prothoracic glands to secrete ECDYSONE

4. Prothoracic glands(PG)• First experimental proof about the importance of

Prothoracic Glands was provided by a Japanese worker, Fukuda in 1940 working with silkworm.

1.Ecdysone is the most common ecdysteroid produced in insects.

2. High doses of β-Ecdysone cause death in insects due to toxic effect it may undergo abnormal moulting.

ECDYSTEROIDS

Most of insects

Some Lepidopteran larvae

In Honey bees and Heteroptera

In Diptera released from the Ovaries and stimulates the fat body to produce Vitellogenin.

In 1954, Butenandt and Karlson for the first time extracted a. steroid hormone, ecdysone in crystalline form Bombyx moori.α-Ecdysone and β- Ecdysone

Present in Cyclorrophous

Diptera Formed by the fusion of Carpora cardiaca, Carpora allata, Prothoracic glands and Hypocerebral ganglion Occur as small ring like tissue supported by trachea around aorta

Secrete puparium hardening

hormone

Controls metamorphosis in flies

5. Weismann's ring/ Ring gland

Weismann's ring

Ring Gland

Hypocerebral Ganglion

OTHER HORMONES

PEPTIDE HORMONES:-It is known to control wide range of Physiological, Biochemical, and Developmental function including water balance, lipid and carbohydrate metabolism, muscle contraction ,reproduction , growth and development

DIURETIC HORMONE (s)It involved in the regulation of Insect Water balance

CHLORIDE-TRANSPORT STIMULATING HORMONE

In Desert Locust, rectum of insect is an important organ, which regulates the ionic balance. It is stimulated by the hormone from Corpora Cardiaca, the Chloride-Transport Stimulating Hormone(CTSH).

Neurohormone -D

Material isolated from CC of Caracius morosus called Neurohormone–D which increasing the frequency of amplitude of Heart Beat, stimulating colour change in Caracius.

PROCTOLINIsolated from Periplanata americana. It acts as an Excitatory Neurotransmitter to modulate Muscle Excitability.

ADIPOKINETIC HORMONE(AKH)It is an Decapeptide isolated from the Locust. AKH in CC of Locust regulates LIPID METABOLISM.

Functions of the Endocrine Glands

Regulation of Molting Determination of form at

Metamorphosis Polymorphism Regulation of Diapause Involvement in Reproduction Regulation of Metabolic Activities

and general body functions Regulation of Behavior

REFERENCESThe Insects: Structure and Function, 5th Edition,2013 - R.F.ChapmanPhysiological Systems in Insects, 2nd Edition,2007 - Marc J. KlowdenThe Insects : An Outline of Entomology, 4th Edition, 2010 -Penny J. Gullan and Peter S. CranstonPrinciples of Insect Physiology, 7th Edition,1972 - V. B. Wigglesworth

Journal of Insect Physiology, Pergamon Press, NYJournal of Insect Science, PAU,Ludhianawww.wiley.com/go/gullan/insects

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